Olivier Absil · 2017-12-11 · We all live in a debris disk! 2nd generation dust (asteroids,...

Olivier Absil

University of Liège

Seminar at OCA – December 6th, 2012

� We all live in a debris disk!� 2nd generation dust (asteroids, comets)

� Dust is luminous (much more than planets)

� Dust is expected in any planetary system

Kuiper belt: 40 K, 50 AU Zodiacal disk: 300 K, 1 AU

Observations Simulations

Earth at 1 AU

Golimowski et al. 2006; Greaves et al. 2005; Schneider et al. 2005; Holland et al. 1998; Stark & Kuchner 2008; Wyatt et al. 2006

T ~ 40 K

T > 300 K

� Prominent far-IR excess

� Easy to resolve (>1”)

� Small near/mid-IR excess

� Difficult to resolve (< 0.1”)

wavelength [µm]

flu

x

???

flu

x

1 10 100

wavelength [µm]1 10 100

� « A mote of dust suspended in a sunbeam »

Picture taken by Voyager 1 in 1990 (40 AU from Earth)

� Spitzer/IRS (5-34 µm)

� Spitzer/MIPS (24 µm)

� Sensitivity� ~1000 zodi (8-12 µm)

� Statistics� ~1% warm excess

� Limited by� Photometric accuracy

� Model of the stellar

photosphere

Beichman et al. 2006; Lisse et al. 2012

� Bright exozodis

resolved only in

favorable cases� Nearby star

� Large telescope

� Ground-based �

large background� Sensitivity ~ 1000 zodi

� Future: JWST/MIRI,

ELT/METIS� Down to a few zodis?

Moerchen et al. 2007; Smith et al. 2009

N band Q band

Principle and first results

�� � �1 � 2�2��� � �⁄

� � �⁄

�

� Disk larger than λ/B � visibility loss� Best detected at short baselines (~10-30m)

Flux ratio

Requires very good accuracy (~1%)

Fully resolved at 10m

Fully resolved at 200m

FLUOR at CHARA IONIC at IOTA

VINCI and PIONIER at VLTI

Absil et al. 2006

� H-band short baseline data (IOTA/IONIC)� No closure phase � not a point-like source� Dust distribution not constrained

Defrère et al. 2011

� Point-like source?� No closure phase signal� RV and astrometry stable� Very low probability for background star

� Stellar wind / circumstellar gas?� A stars: very weak winds (~10-12..14 M

�/yr)

� Free-free emission: should be stronger at mid-IR� Ae/Be phenomenon: no evidence for Hα emission

� Circumstellar dust?� Thermal emission & reflected flux

� New, unknown phenomenon?

� H- and K-band interferometry

� N-band nulling interferometry (MMT/BLINC)

� Archival near- to mid-IR spectro-photometry

Defrère et al. 2011

� Bayesian χ2 analysis of

large parameter space� Grains < blowout size

� Hot grains (> 1000 K)

� Presence of carbons ≥ 10%

� Distance: ~ 0.1 – 0.5 AU

� Steep density power law:

α < −3 � ring?

� Mass: ~2×10-9 MEarth

� Luminosity: ~5×10-4 Lstar

Defrère et al. 2011

Debris disk

Holland et al. 1998

200 AU

0.2 AU3 × 10-3 M⊕3 × 10-5 L�

2 × 10-9 M⊕5 × 10-4 L�

� Local production?

� Connection to outer disk?� Poynting-Robertson drag?� Multiple scattering of comets?

0.5 AU100 AU

Vega:

455 Myr,

46.7 MEarth

Vega:

700 Myr,

46.7 MEarth

(Monnier12)

Bonsor et al. 2012

� Isolated event?� Large collision (e.g. Earth-

Moon)

� Break-up of giant comet

� Dynamical perturbations?� Falling Evaporating Bodies

▪ Asteroid belt disturbed by

MMR with massive planet

� Late Heavy Bombardment

▪ Global rearrangement

� Statistical study may help

CHARA/FLUOR observations

� Magnitude-limited sample� (All) northern stars with far-IR excess and K<4

� ~ same amount of “non-dusty” stars

� Evenly spread between spectral types A, F and G-K

� Diameters predicted from surface-brightness relationships

Dusty Clean Total <Kmag>

A 8 4 12 2.4

F 6 9 15 2.7

GK 8 7 15 2.7

Total 22 20 42 2.6

Detection, many points Non-detection, few points

Too-good-to-believe High χ2

Absil et al., in prep

� Wavy pattern in

visibilities (� large χ2)

� Confirmed with

coronagraphy� 330 mas separation

� 2% flux ratio

Mawet et al. 2011

tau Cet zet Aql

Caveat: not all excesses followed up!

� Mean sensitivity(at 1σ) = 0.3%

� 0.3 < χr2 < 3 for

most targets

� Distribution corelooks ~ Gaussian� No target with

significance < -3σ

� Detection threshold set at 3σ� 12 excesses out of

41 stars � ~30%

Absil et al., in prep

eps Cep

50% 21% 20%0%

10%

20%

30%

40%

50%

60%

70%

A F GK

Ex

ozo

di d

ete

ctio

n f

req

ue

ncy

41% 16%0%

10%

20%

30%

40%

50%

60%

Cold dust No cold dust

Ex

ozo

di d

ete

ctio

n f

req

ue

ncy

Absil et al., in prep

38% 75%50% 0%38% 0%0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Cold dust No cold dust

Ex

ozo

di d

ete

ctio

n f

req

ue

ncy

A stars

F stars

GK stars

Absil et al., in prep

-2.00%

-1.00%

0.00%

1.00%

2.00%

3.00%

4.00%

0.0 50.0 100.0 150.0 200.0 250.0 300.0 350.0

K-b

an

d e

xce

ss

v sin i [km s-1]

Absil et al., in prep

-2.00%

-1.00%

0.00%

1.00%

2.00%

3.00%

4.00%

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00

K-b

an

d e

xce

ss

Age [Gyr]

Absil et al., in prep

Millan-Gabet et al. 2011

More KIN follow-up to come…

First results with VLTI/PIONIER

� New targets: Spitzer, Herschel cold disks

� Go fainter� Refurbished FLUOR � “JOUFLU”� New camera, upgraded optics� Expect high-precision down to K~5 (good conditions)

� Go South� PIONIER at VLTI� High-precision V2 down to H~5 (good conditions)� Same fringe scanning principle as FLUOR

� 6 (short) baselines at a time � huge gain in speed

� Goal: no bias on inner/outer disk connection study

� One non-dusty “control” star for each dusty target� Same spectral type

� Similar magnitude

� Proximity on the sky

� No binaries, bloated stars

� Distribute evenly between A, F and G-K

� Final sample: ~100+100 stars (whole sky)

� Dispersed fringes with PIONIER (soon FLUOR)� Flux ratio measurements across H and/or K band

� Direct constraint on dust temperature

Defrère et al. 2012

bet Pic

� A lot of time spent on TF stability analysis� DRS validated

� PIONIER stability validated

� VLTI polarization effect identified

� V2 accuracy on spec after correction

� 4 × 3n awarded in 2012� 3 runs carried out

� 74 stars observed

LBTI?